This invention relates to thermotropic crosslinkable polyesters capable of forming a anisotropic melt and having approximately 1 to 40 mole percent of units derived from allylically substituted hydroxybenzoic acid and to a process for preparing a shaped article of the polyesters.
It is known in the art to prepare polymers from ethylenically unsaturated hydroxybenzoate esters. U.S. Pat. No. 3,141,903 to Fertig et al discloses a monomer of the formula ##STR1## wherein X is an ethylenically unsaturated group selected from the group consisting of acrylyloxy, acrylyloxyalkyl, methacrylyloxy, and methacrylyloxyalkyl. However, these monomers are said to undergo vinylic type polymerization rather than polyesterification, and therefore no pendant allylic groups remain and the polymer which results is therefore not crosslinkable.
It is also known to produce polymers other than polyesters from allyl substituted phenols or phenolic derivatives. Canadian Patent No. 569,348 to D'Alelio discloses a polymerizable allyl phenyl monomer of the formula: EQU CH.sub.2 .dbd.CH--CH.sub.2 --Ar--O--X,
wherein Ar is an arylene radical and X may be epoxyalkyl, hydroxyalkyl, dihydroxyalkyl, chloroalkyl or --CH.sub.2 COOH. Polymers prepared from the monomer of D'Alelio are said to contain oxyalkylene rather than ester linkages, and pendant allylic groups.
Also, Japanese Pat. No. 0082719 discloses a polyphenylene ether having pendant allyl groups. The modification of the polymer is said to permit easy graft copolymerization, epoxidation, or halogenation. However, neither of these patents appears to disclose polymers which have polyester linkages and which are capable of forming an anisotropic melt which may be crosslinked.
It is also known to prepare aromatic copolyesters of hydroxynaphthoic acid and hydroxybenzoic acid. U.S. Pat. Nos. 4,337,190 and 4,161,470 to Calundann and U.S. Pat. No. 4,429,105 to Charbonneau (assigned to the assignee of the present application) disclose wholly aromatic copolyesters of the above acids which exhibit a thermotropic melt phase. However, the copolymers of the Calundann and Charbonneau patents contain no pendant allylic groups and are therefore not crosslinkable.
It is also known to produce wholly aromatic monomers having liquid crystalline central portions and crosslinkable end groups. For example, U.S. Pat. Nos. 4,440,945 and 4,452,993 to Conciatori et al disclose wholly aromatic monomers which are terminated with acetylene and acrylic acid, respectively, and which are capable of forming an anisotropic melt which may be crosslinked. However, inasmuch as these oligomers are of low molecular weight, they have low melting temperatures and are therefore unstable at high temperatures.
Accordingly, it is an object of the present invention to provide thermotropic crosslinkable polyesters containing recurring units derived from allylically substituted hydroxybenzoic acid.
It is a further object of the present invention to provide thermotropic crosslinkable polyesters containing recurring units derived from allylically substituted hydroxybenzoic acid which exhibit anisotropy in the melt phase and which may be formed into a shaped article and crosslinked to produce an article which is heat stable at temperatures in excess of the melting point of the uncrosslinked polyester article.
It is a still further object of the present invention to provide a thermotropic crosslinkable polyester containing recurring units derived from allylically substituted hydroxybenzoic acid copolymerized with hydroxybenzoic and/or hydroxynaphthoic acids free of allylic substitution and/or substantially stoichiometrically balanced amounts of aromatic diols and aromatic diacids.
It is a still further object of the invention to provide a process for preparing a crosslinked shaped polyester article from a polyester containing recurring units derived from allylically substituted hydroxybenzoic acid.
These and other objects, as well as the scope, nature and utilization of the invention, will be apparent from the following detailed description of the present invention and appended claims.